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02-18-2018, 06:55 PM | #1 |
Member
Join Date: Nov 2010
Posts: 48
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Is my coil bad?
I've been trying to get my '30 Tudor back on the road after a 2 yr. hiatus & I think I have a bad coil. I'm not getting any spark between the points or from the coil.
I've tested the coil (an old oil filled, repo script coil) with my multi-meter & on the 20 ohm scale I get these readings: between the + & - terminals scale reads a 0 ohm short between + or - to center reads 7.9-8 ohms between + or - to case shows open circuit. One of my manuals says the short between + & - terminals indicates a bad coil. Also coil gets hot after leaving ignition switch on while trouble shooting. I've check & adjusted all the other parts of the ignition & it all checks out OK. Think my coil is bad or have another problem? Thanks! Bob |
02-18-2018, 07:40 PM | #2 |
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Join Date: Oct 2013
Location: Syracuse,NY
Posts: 264
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Re: Is my coil bad?
Try another condenser.
If that does not work get another coil from a local auto parts store or from one of the A parts vendors. |
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02-18-2018, 07:56 PM | #3 |
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Join Date: May 2010
Location: Mpls, MN
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Re: Is my coil bad?
Coil case should be isolated, so that's fine.
A 6 volt coil should have about 1 1/2 ohms between the primary terminals, and this is hard to measure on many cheap meters. Ground the red wire on the coil primary terminal and see if your ammeter reads about 4 amps. |
02-18-2018, 09:24 PM | #4 |
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Join Date: Jun 2017
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Re: Is my coil bad?
2X on what Tom said.
Try his suggestion on the ammeter. Also, if the coil is getting warm when the ignition is turned on then there is likely proper resistance and not a dead short. If it was a dead short, then it would more likey blow a fuse if your car is equipped with a fuse. Some other things to check: Capacitor might be shorted. Take it out and put the ohm meter on it. If it shows completely open on an ohm meter or causes the needle to jump, then the cap is likely good, If it shows any low value of resistance, then it is probably toast, and would keep spark from happening. You should also make sure that the armored cable coming from the ignition swich is not turned in too tightly. If it is too tight, it bottoms out witha short and literally bypasses the points and would cause the kind of problem you are having. |
02-19-2018, 10:14 AM | #5 |
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Join Date: Dec 2010
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Re: Is my coil bad?
Armoured cable should be turned in only about 2 or 3 turns.
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02-19-2018, 12:17 PM | #6 |
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Location: Largo Florida
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Re: Is my coil bad?
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Turn on key with points open, should have battery [6v] voltage at open point arm. If not the cable may well be screwed in too far or some other problem somewhere in the primary circuit. If you remove the secondary lead and place it near a good ground, open and close points with key on there should be a good spark. [ I don't know how you made the checks]. The info about checking the coil is of course good info. |
02-19-2018, 01:47 PM | #7 |
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Join Date: Feb 2017
Location: Northern Idaho
Posts: 282
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Re: Is my coil bad?
Were the ohm readings taken with the coil connected to the vehicle? This may alter the results and advice.
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02-19-2018, 01:56 PM | #8 |
Member
Join Date: Nov 2010
Posts: 48
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Re: Is my coil bad?
Ohm readings made with coil out of car & disconnected.
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02-19-2018, 02:37 PM | #9 |
Member
Join Date: Nov 2010
Posts: 48
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Re: Is my coil bad?
Thanks for the suggestions, I'll give them a try this afternoon or Tuesday.
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02-19-2018, 03:34 PM | #10 |
Senior Member
Join Date: Feb 2017
Location: Northern Idaho
Posts: 282
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Re: Is my coil bad?
I would say the coil is bad, given your initial readings.
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02-19-2018, 03:52 PM | #11 |
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Join Date: May 2010
Location: Southern California
Posts: 3,131
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Re: Is my coil bad?
The attached article may be of help isolating an electrical fault.
Tom Endy |
02-19-2018, 06:57 PM | #12 |
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Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
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Re: Is my coil bad?
One day I was working on my car and when I installed the instrument panel I just happened to feel the coil getting warm, even though the key was off. The repro switch terminal was rubbing the gas tank and shorting to ground. I had to bend the switch terminals to the side.
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